Evaluating phase-tensor-derived geoelectrical strike for two-dimensional magnetotelluric inversion in a geothermal field
DOI:
https://doi.org/10.58524/jograv.v1i2.185Keywords:
Magnetotelluric inversion, Phase tensor, Geoelectrical strike, Dimensionality analysis, Geothermal resistivityAbstract
This study evaluates the effect of phase-tensor-derived geoelectrical strike on 2D MT inversion by comparing three processing scenarios: geoelectrical-strike-rotated data, geological-strike-rotated data, and unrotated statically corrected data. The analysis was based on secondary MT data in EDI format from the “ABL” geothermal field. Phase-tensor parameters, including (ɸmax), (ɸmin), and skew angle (β), were used to evaluate scale-dependent dimensionality and determine station-specific geoelectrical strike directions. The dominant geological strike derived from mapped structures is approximately N35°W, whereas geoelectrical strike varies markedly between stations, indicating significant lateral electrical complexity. Representative stations show transitions from predominantly 1D behavior at higher frequencies to 2D and locally 3D responses at lower frequencies. Two-dimensional inversions performed using the three datasets produce different resistivity distributions, particularly in the geometry and continuity of shallow conductive zones. The models rotated using phase-tensor-derived geoelectrical strike show the closest qualitative consistency with the available geological sections and with the shallow resistivity architecture inferred from 1D inversion. The resulting resistivity structure includes conductive zones consistent with hydrothermal alteration, moderately resistive domains that may represent permeable geothermal units, and deeper resistive bodies interpreted as basement-related structures. The results demonstrate that strike selection can materially influence 2D MT imaging and subsequent geothermal interpretation. Phase-tensor analysis therefore provides a useful framework for constraining dimensionality and selecting strike orientation prior to 2D inversion, although residual 3D effects and inversion non-uniqueness remain important limitations.
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